• Journal of the Korea Society of Computer and Information
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• v.28 no.4
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• pp.105-112
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• 2023

In this paper, we propose a new method for displaying colored defects by measuring the relative density with the wide-area and local densities of X-ray. The relative density of one pixel represents a relative difference from the surrounding pixels, and we also suggest a colorization of X-ray images representing these pixels as normal and defective. The traditional method mainly inspects materials such as plastics and metals, which have large differences in transmittance to the object. Our proposed method can be used to detect defects such as sprouts or holes in images obtained by an inspection machine that detects X-rays. In the experiment, the products that could not be seen with the naked eye were colored with pests or sprouts in a specific color so that they could be used in the agricultural product selection system. Products that are uniformly filled with a single ingredient inside, such as potatoes, carrots, and apples, can be detected effectively. However, it does not work well with bumpy products, such as peppers and paprika. The advantage of this method is that, unlike machine learning, it doesn't require large amounts of data. The proposed method could be applied to a screening system using X-rays and used not only in agricultural product screening systems but also in manufacturing processes such as processed food and parts manufacturing, so that it can be actively used to select defective products.

• Progress in Medical Physics
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• v.21 no.1
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• pp.93-98
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• 2010

The aim of this work was to establish the methodology for event positioning by measuring depth of interaction (DOI) information and to evaluate the system sensitivity and spatial resolution of the new detector for I-125 and Tc-99m imaging. For this purpose, a Monte Carlo simulation tool, DETECT2000 and GATE were used to model the energy deposition and light distribution in the detector and to validate this approach. Our proposed detector module consists of a monolithic CsI(Tl) crystal with dimensions of $50.0{\times}50.0{\times}3.0\;mm^3$. The results of simulation demonstrated that the resolution is less than 1.5 mm for both I-125 and Tc-99m. The main advantage of the proposed detector module is that by using 3 mm thick CsI(Tl) with maximum-likelihood position-estimation (MLPE) method, high resolution I-125 imaging and high sensitivity Tc-99m imaging are possible. In this paper, we proved that our new detector to be a reliable design as a detector for a multi-energy SPECT.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1103-1105
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• 2015

Leaked Radioactive source in nuclear power station, radiation related facilities and the aging nuclear power plant for the dismantling must need to detect and remove early to prevent major accidents. In this paper, we implemented a single sensor-based gamma-ray detectors stereo which can provide the distance to the radiation source, a direction and doserate information for fast and efficient decontamination work the radiation source. And we have carried out an algorithm development for high-speed detection of the detection equipment. Two detectors are required for stereo structure for obtaining the distance information of the radioactive source, but we designed the only sensor-based detection device for the weight reduction. We have extracted the region of interest and obtained the distance calculation result and distribution of radiation source in order to minimize a stereo image acquisition time. Detection time of the algorithm showed a shorter time of about 41%.

• Journal of the Korean Society of Radiology
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• v.17 no.1
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• pp.11-16
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• 2023

In preclinical positron emisson tomography(PET), spatial resolution degradation occurs outside the field of view(FOV). To solve this problem, a depth of interaction(DOI) detector was developed that measures the position where gamma rays and the scintillator interact. There are a method in which a scintillation pixel array is composed of multiple layers, a method in which photosensors are arranged at both ends of a single layer, a method in which a scintillation pixel array is constituted in several layers and a photosensor is arranged in each layer. In this study, a new type of DOI detector was designed by analyzing the characteristics of the previously developed detectors. In the two-layer detector, different sizes of scintillation pixels were used for each layer, and the array size was configured differently. When configured in this form, the positions of the scintillation pixels for each layer are arranged to be shifted from each other, so that they are imaged at different positions in a flood image. DETECT2000 simulation was performed to confirm the possibility of measuring the depth of interaction of the designed detector. A flood image was reconstructed from a light signal acquired by a gamma-ray event generated at the center of each scintillation pixel. As a result, it was confirmed that all scintillation pixels for each layer were separated from the reconstructed flood image and imaged to measure the interaction depth. When this detector is applied to preclinical PET, it is considered that excellent images can be obtained by improving spatial resolution.

• Journal of the Korean Society of Radiology
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• v.16 no.6
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• pp.703-708
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• 2022

A detector module measuring the depth of interaction(DOI) was designed to improve the spatial resolution of positron emission tomography(PET). The scintillation pixel array consists of two layers, and a light guide is inserted between the layers to make the light generated through the gamma-ray event different for each layer. There are four light guides, and one light guide is designed to be coupled to a 2 × 2 array of scintillation pixels. The light generated from the top layer is moved to the photosensor with a wider distribution through the light guide, and the light generated from the bottom layer is incident on the photosensor with a narrower distribution than the top layer. When a flood image is reconstructed based on the signals obtained from the photosensor by different distributions, scintillation pixels are imaged at different positions for each layer. To verify this, a DETECT2000 simulation tool that simulates the behavior of light in a scintillator was used. By designing a scintillation pixel array, a detector consisting of a light guide and a photosensor, a gamma ray event was generated in all scintillation pixels to obtain a flood imgae. As a result, it was confirmed that the top and bottom layers were imaged at different positions and completely separated. When this detector is applied to PET, it is considered that image quality can be improved through imporved spatial resolution.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.12
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• pp.1535-1541
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• 2019

To carry out safe and rapid decontamination in radiological accident areas, acquisition of various information on radiation sources is needed. In particular, to figure out the location and distribution of radiation sources is essential for rapid follow-up and removal of contaminants as well as minimizing worker damage. The radiation distribution detection device is used to obtain the position and distribution information of the radiation source. In the case of a radiation distribution detection device, a detection sensor unit is generally composed of a single sensor, and the detection range is limited due to the physical characteristics of the single sensor. We applied a calibration detector for controlling the detection sensitivity of a single sensor for radiation detection and improved the limited detection range of radiation dose rate. Also, gamma irradiation test confirmed the improvement of radiation distribution detection range.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.324-326
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• 2006

CCD형 영상소자는 방사선 피폭 시 표면과 격자내부에 모두 손상을 받게 되며, 감마방사선이나 X선과 같은 고에너지의 이온화 방사선에 노출될 경우 격자 실리콘 내부에 전자-전공쌍(Electron-hole pair, EHP)이 발생된다. 이러한 EHP는 CCD의 순간 출력 광전류로 변환되어 백색 화소 형태의 영상잡음으로 가시화되며, 이 화소 수는 피폭 방사선량에 비례하여 증가하는 특성을 지니고 있다. 따라서 출력 영상정보를 분석하면 조사된 방사선의 양과 특성을 측정할 수 있다. 본 연구에서는 CCD를 이용하여 가상의 방사능 물질 누출 공간에서 방사선원의 방향과 거리정보를 고속으로 탐지하기 위한 장치와 고속 측정 알고리즘을 구현하고 실제 방사선장에서 실증시험을 수행하였다. 방사선 탐지기는 콘형 납 콜리메이터(Collimator)와 가시광 변환용 신틸레이터(CsITl) 및 차폐체로 구성된 센서부와 제어 및 방사광 신호처리를 수행하는 PC부로 구성된다. 감마방사선($^{60}Co$) 방사선장 실증시험에서 방사선원간 거리 83cm에서 측정된 거리 탐지는 5.3%의 오차로 확인되었다. 이 방사선 탐지기는 임의의 고방사선 누출사고에 대한 초기대응 작업을 수행하기 위한 무인 이동로봇용 방사선 탐지기로 활용이 가능하다.

• The Korean Journal of Nuclear Medicine
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• v.32 no.4
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• pp.365-373
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• 1998

Purpose: The conventional gamma camera is not ideal for scintimammography because of its large detector size (${\sim}500mm$ in width) causing high cost and low image quality. We are developing a small gamma camera dedicated for breast imaging. Materials and Methods: The small gamma camera system consists of a NaI (T1) crystal ($60 mm{\times}60 mm{\times}6 mm$) coupled with a Hamamatsu R3941 Position Sensitive Photomultiplier Tube (PSPMT), a resister chain circuit, preamplifiers, nuclear instrument modules, an analog to digital converter and a personal computer for control and display. The PSPMT was read out using a standard resistive charge division which multiplexes the 34 cross wire anode channels into 4 signals ($X^+,\;X^-,\;Y^+,\;Y^-$). Those signals were individually amplified by four preamplifiers and then, shaped and amplified by amplifiers. The signals were discriminated ana digitized via triggering signal and used to localize the position of an event by applying the Anger logic. Results: The intrinsic sensitivity of the system was approximately 8,000 counts/sec/${\mu}Ci$. High quality flood and hole mask images were obtained. Breast phantom containing $2{\sim}7 mm$ diameter spheres was successfully imaged with a parallel hole collimator The image displayed accurate size and activity distribution over the imaging field of view Conclusion: We have succesfully developed a small gamma camera using NaI(T1)-PSPMT and nuclear Instrument modules. The small gamma camera developed in this study might improve the diagnostic accuracy of scintimammography by optimally imaging the breast.

• Journal of the Korean Society of Radiology
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• v.15 no.1
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• pp.1-7
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• 2021

In order to acquire an image in a positron emission tomography, it is necessary to draw the position coordinates of the scintillation pixels of the detector module measured at the same time. To this end, in a detector module using a plurality of scintillation pixels and a small number of photosensors, it is necessary to obtain a flood image and divide a region of each scintillation pixel to obtain a position of a scintillation pixel interacting with a gamma ray. Alternatively, when the number of scintillation pixels and the number of photosensors to be used are the same, the position coordinates for the position of the scintillation pixels can be directly acquired as digital signal coordinates. A method of using a plurality of scintillation pixels and a small number of photosensors requires a process of obtaining digital signal coordinates requires a plurality of photosensors and a signal processing system. This complicates the signal processing process and raises the cost. To solve this problem, in this study, we developed a method of obtaining digital signal coordinates without performing the process of separating the planar image and region using a plurality of flash pixels and a small number of optical sensors. This is a method of obtaining the position coordinate values of the flash pixels interacting with the gamma ray as a digital signal through a look-up table created through the signals acquired from each flash pixel using the maximum likelihood function. Simulation was performed using DETECT2000, and verification was performed on the proposed method. As a result, accurate digital signal coordinates could be obtained from all the flash pixels, and if this is applied to the existing system, it is considered that faster image acquisition is possible by simplifying the signal processing process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1865-1870
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• 2011

In this paper, we propose an effective method that automatically detects flaws in air deck by using non-destructive testing. First, Gamma correlation transform, 7 ${\times}$ 7 and 13 ${\times}$ 13 Sobel mask apply to the image of air deck acquired non-destructive testing in order to detect the edge of the image. Second, the edge detection area is smoothed and corrected by mean binarization method. Finally, the region of flaws in air deck is detected by a labeling method after removing the noise by the erosion and the dilation operation. In experimental results, we showed that the proposed detection method is effective in air deck.